1. Field of the Invention
This invention pertains to the field of electromagnetic power combining (either CW or pulsed), particularly at microwave frequencies, by means of coupled cavities containing power generating devices.
2. Description of the Prior Art
A prior art search uncovered the following references:
U.S. Pat. No. 3,628,171 illustrates early work done in the field of microwave power combining, wherein a single rectangular-cross-section cavity was employed with several diodes coupled to the cavity. The present invention utilizes more than one cavity, and in addition, preferably uses a cavity having a circular rather than rectangular cross-section.
U.S. Pat. Nos. 3,931,587 and 4,121,174 depict microwave cavity combiners having circular cross-sections. These cavities are of the general type used in the present invention. However, these patents do not illustrate the use of more than one cavity as in the present invention.
U.S. Pat. No. 4,147,994 discloses a power combiner for solid state oscillator circuits comprising a combination of a central cavity and several subcavities; coupled to the latter are several solid state oscillator circuits. All the subcavities are tuned to reasonate at the same frequency, unlike in the present invention where several mutually coupled cavities are intentionally tuned to operate at slightly offset natural frequencies. The present invention obtains a bandwidth improvement over this patent.
U.S. Pat. No. 4,175,257 discloses a modular microwave power combiner wherein each module comprises a central resonant cavity to which the power of several microwave diode amplifiers is coupled. The individual modular units are spaced apart by one half wavelength to allow parallel electrical coupling of all the resonant cavities. All of the individual modular units are tuned to operate at the same frequency, unlike in the present invention where the resonant frequencies of the individual cavities are intentionally offset. The present invention obtains a bandwidth improvement over this patent.
Proposal No. P-26189 for "GaAs IMPATT Diode Power Combining Techniques", Vol. 1 Technical, submitted by Ford Aerospace & Communications Corporation (the assignee of the instant invention) in response to RFP F33615-80-R-1015 to the United States Air Force Jan. 15, 1980, states on page 2-45 that outputs from two or more TM.sub.010 cavities can be combined with potential for increased bandwidth with the proper choice of cavity-to-cavity coupling "as in a multisection bandpass filter". However, the reference does not disclose any of the following features of the present invention: the resonant frequencies of the individual cavities in the present invention are offset; the entire combination of cavities is injection locked; there is mutual coupling among all the cavities; the combiner is operated in a single mode, preferably the dominant mode (in fact, the reference discloses the opposite, i.e., the excitation of additional cavity modes).
Secondary references are U.S. Pat. Nos. 3,378,789; 3,582,813; 3,662,285; 3,733,560; 3,783,401; 3,873,934; 3,943,463; 3,962,654; 4,034,314; 4,075,578; 4,083,016; 4,090,152; 4,097,817; 4,143,334; 4,172,240; 4,188,590; and 4,189,684.